My take

I get what ur saying. Personally i think its bc of culture, is very purity type. Hence why the bottoms are almost always virgins as well. They think them denying their own pleasure makes them modest and pure. Thats what ive seen at least, one that note I also enjoy how the seme while he is stoic, he is still expressive, he smirks, blushes, etc. So many semes have stuch a blank straight face during sex its off putting.

First we have to remember that this is just fiction, but honestly I know what you mean and I'm also not a fan of this. When it comes to irl it all depends on what couple decides and knowing your partner well. There are people who engage in cnc (consensual no-consent), in this setting "no" in fact does not mean no, it's like role-playing but as all kinks it should be discussed beforehand and only done with an established safe word (so the real "no"). If cnc is not the case then personally I can't imagine to keep going if my partner keeps saying "no" even if they look like they're "into it" and would not trust anyone who thinks differently. When it comes to fiction I rlly don't know why it's such a common trope but I would assume it's an author portraying their own kinks and it's (from my experience) not akin to reality

First, I also hear you, and I also agree with it being culture based. Like you’re not really supposed to enjoy it because it’s dirty or forbidden so you’re supposed to deny it to an extent like. I could be way off base, but that’s the vibe I get. I also have found a lot of times it’s more embarrassment from cumming first of at all in some stories.

Ive considered the embarrassment/overstimulated part as well but that ultimately from my perspective that falls under communication and consent tbh, unless they enoy it but are embarrassed then its back under cultural stuff bc why would they be embarrassed? Realistically one of them is always gonna finish first, and while being embarrassed as a first timer is understandable bc well, you arent used to things. At a certian point you learn what to expect out of your body and get over that or you feel a sense of shame finishing first which is why you continue to feel embarrassment right? And that just leads back to the "i shouldnt be so lustful" or "i lack stamina" route right? Which is why i just sorta umbrellaed everything together bc overstimulation is generally a kink which involves consent and what people feel embarrassed about is usually cultural.

as everyone has mentioned, it's definitely cultural &/or kink based. i'm japanese & i remember getting into arguments with ppl over the anime "yes, no or maybe?" that story perfectly portrays the dynamic you're talking about. majority of ppl were saying how unfortunate of a story it was bc it's noncon & it's literally not. the uke is a massive tsundere & he's saying "no" throughout their convos & especially during sex, BUT he fully consents to it. the whole plot is that he's a double faced contrarian & puts on acts, but ppl thought he was actually getting raped after the 2 guys had a whole heart to heart confessional speech lol. anyways, it pretty much can be a mindset (tsundere), kink, dirty talk, hiding vulnerability &/or a purity thing. to simplify, there's loosely 2 sides to this. 1. it probably stems from the ingrained social norm in asian culture to be modest, pure & chaste. you don't want to seem experienced or they'll think you're kinda slutty. this honestly dates back to european history too with nobility & how you can't wear your heart on your sleeve. 2. "yes" & "no" a lot of times are interchangeable during sex. it's not that deep & ppl just say either to turn each other on i guess.
japanese ppl tend to walk on egg shells as a culture & are very sensitive to boundaries. the common person would know the difference between consent, noncon, & kink, but anyone who ignores it & takes advantage of it are rapists for sure.

Yeah I understand what you’re saying and it honestly comes down to fiction vs. reality. In fiction (esp considering this is eastern asian), they want to preserve purity culture by making the uke deny sex as if it’s something disgusting. It also ties into the temptation of forbidden things and also kinda an instinctual (animalistic?) kink bc of the idea that you’re saying no but your body keeps wanting more. In reality, these types of kinks are usually discussed beforehand & boundaries are set so the person is more certain on when their partner’s no means yes (cnc).

imo the way this bl handles it is completely different from other bls. In this bl, you can tell that Yuan wants it even if he says no bc we see him be excited before a play and happy and well taken care of after a play. And in this chapter, we see that the ml actually stopped and reassured Yuan when Yuan actually was feeling scared. In other bls, we see this exact same situation but handled completely differently. The seme typically continues on with the idea of someone walking in even when the uke is clearly scared. I feel like the difference lies in the way that in typical bls, the seme assumes the uke likes a certain foreplay/kink bc their body is aroused (even though the rest of their body language is saying no) while in this bl, yuan’s entire body language is saying yes and he’s very happy about their plays outside of when they’re having sex. Again, this is with a fictional viewpoint bc you still definitely need to talk out at least the basic stuff before getting to that level.

Sorry kinda went on a somewhat unrelated tangent there, this topic can be discussed in so many different ways so I got a little excited :>

I agree also thanks for explaining (=・ω・=)

You cooked with this I forgot the purity culture that East Asians have.